The present invention relates to a web guide device operable to permit a web of material, particularly a paper web, to be wound about at least one return pulley.
Although in the following description reference will only be made to a cigarette-making machine, it is clear that the web guide device forming the subject of the present invention can be applied to any of those machines in which strip or web material, in particular paper, is made to advance along a non-rectilinear path to which it is difficult for an operator to gain access.
Cigarette-making machines normally include a supply unit within which a web of paper unwound from a reel is supplied through a plurality of operator units until it reaches a deflector pulley about which the strip is wound, following which it then proceeds horizontally over a bed along which the web is progressively folded transversely until it forms a continuous cylinder. Near to the said deflection pulley the section of the paper web which advances along the said bed receives a continuous layer of shredded tobaco which becomes enclosed within the said continuous cylinder in such a way as to form a continuous cigarette rod.
When, during the operation of the cigarette-making machine, the paper web breaks upstream of the said return pulley, a sensor normally provided along the path followed by the web automatically interrupts the operation of the cigarette-making machine thereby permitting an operator to intervene.
Among the various operations which this latter must perform to put the machine back into operation, one of the most complicated is certainly that consisting in rewinding the paper web about the said return pulley and then threading it through the normally narrow space between the said bed and the end of a conveyor which supplies the said layer of tobacco.
Such operation, which is difficult to perform on a cigarette-machine forming a single rod of cigarette, becomes almost impossible when it has to be performed on a twin rod cigarette making machine, that is to say one capable of simultaneously producing two rods of cigarette. In fact, in this machine, there are two paper webs and these have to be wound about respective return pulleys which are positioned coaxially to one another, before advancing along the bed on which the rods are formed.
Consequently, one of the said two return pulleys is completely obscured by the other as far as the operator who has to operate thereon is concerned, and therefore is substantially inaccessible. A known web guide device is described in Italian patent application No. 50484-A-79 filed in the name of the same Applicant, G.D.S.P.A, in which the winding of the web about the said pulley is performed in an automatic manner. In this device the said pulley and other fixed and movable elements located close to the pulley itself along the path provided for the web are hollow and are provided with holes in the region of contact with the web.
The interior of these members communicate with a vacuum source, and the web can be made to follow around the said pulley until it reaches the rod forming bed simply by making the end of it adhere to the first and therefore most accessible of the said movable suction members.
A device of the type described, although resolving the described problems in a quite satisfactory manner nevertheless is rather complicated and expensive to manufacture. Moreover, it has been established that this device, after a certain period of continuous operation of the cigarette-making machine, can become less efficient because of obstruction of some of the said suction holes.
These holes must, in fact, necessarily be made of extremely small dimensions so as not to cause deformation or damage to the web however, they can sometimes become obstructed, after long use, by dust or fragments of paper released from the web itself.